Hard and soft capsules comprising pullulan are known.
WO2005105051 discloses a hard capsule comprising a conventional pullulan grade in an amount of 85% to 90% by weight, potassium chloride in an amount of 1.0% to 1.5% by weight, carrageenan in an amount of 0.1% to 0.4% by weight, one or more surfactants in an amount of 0.1% to 0.2% by weight and water in an amount of 10% to 15% by weight over the weight of the capsule. Thanks to the addition of a particularly selected setting system, WO2005105051 capsules are inter alia endowed with an improved chemical stability (e.g. no polymer cross-linking as with conventional gelatin). WO2005105051 does not disclose or suggest the use of any specific pullulan grade or the advantages following therefrom.
EP1072633 discloses compositions based on pullulan and a setting system for the use e.g. in manufacturing soft or hard capsules. EP1072633 stresses the importance of the addition of an appropriate setting system whereas no indication is given to select a specific pullulan grade or the advantages following therefrom.
EP1157691 discloses pullulan compositions for use e.g. in manufacturing soft or hard capsules with improved surface properties. The advantage is obtained by using a surfactant of pharmaceutical or food quality. EP1157691 does not disclose or suggest the use of any specific pullulan grade or the advantages following therefrom.
EP1398346 discloses the manufacturing of a high pullulan content shaped products (such as hard capsules) comprising α,α-threalose and a pullulan having an average molecular weight between 20,000 and 4,000,000 Dalton, preferably between 50,000 and 2,000,000 Dalton, in an amount of 30% or higher on a dry solid basis. The presence of α,α-threalose is praised as the key factor to impart the final products with properties such as stability to the change of humidity, transparency, gloss, and solubility in water. Although the use of PI-20, PF-10 and PF-20 pullulan grades is disclosed, no indication is given to select other specific and more advantageous pullulan grades.
JP5-65222-A describes a soft capsule, capable of stabilizing a readily oxidizable substance enclosed therein, exhibiting easy solubility, and being able to withstand a punching production method. The soft capsule is obtained by blending a capsule film substrate such as gelatin, agar, or carrageenan with pullulan. No indication is given to select a specific pullulan grade or the advantages following therefrom.
The hard capsule shells disclosed in the prior art present certain drawbacks, notably a non-fully satisfactory shell mechanical strength (i.e. shell brittleness) at shell low loss-on-drying, or “LOD.” Improving this property is a particularly desirable goal for pullulan hard capsule shells. Pullulan is in fact more sensitive than other materials (e.g. gelatin or HPMC) to low moisture conditions. This sensitivity impinges upon increased shell brittleness at low water content. Unsatisfactory brittleness means higher manufacturing losses, a poorer quality and global higher costs. On the other hand, reducing LOD of the shell might be desirable to encapsulate those active principles and natural or synthetic substances that are sensitive to water. A shell low LOD is also obtained when hard shells are filled with hygroscopic substances that make the shell moisture to migrate from the shell to the filling so as to simulate a further drying of the shell.
Accordingly, one object of the present invention is therefore the provision of pullulan hard capsule shells and capsules which overcome the drawbacks of the prior art. In particular, one object of the present invention is the provision of new pullulan hard shells and capsules that with respect to prior art pullulan hard capsule shells present improved characteristics in terms of shell mechanical properties especially at low shell LOD levels, and an equally good or improved shell dissolution profile, shell transparency, capsule surface static and gliding properties, absence of unpleasant smell, capsule compatibility with automatic high speed capsule filling equipment.
Another object of the invention is to provide a dip-molding manufacturing process that allows for the manufacture of the improved hard capsule shells as above, in an easy and cost-effective manner and that allows maintaining capsule dimension specificities during production.